Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated
  • C23C22/80—Pretreatment of the material to be coated with solutions containing titanium or zirconium compounds
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling

Definitions

• the invention relates to an improved method for cleaning and degreasing and activating composite parts made of iron or steel and zinc or galvanized steel or aluminum or aluminized steel before a subsequent phosphating treatment of the same, at elevated temperatures and with the aid of aqueous cleaner and / or activation solutions.
• Composite parts of this type are increasingly being used by the automotive industry in the construction of automobile bodies in order to achieve improved corrosion protection of the bodies.
• the iron materials or steel sheets commonly used for body construction are used in combination with both electrolytic and hot-dip galvanized steel.
• zinc alloys are becoming established for this purpose, which can contain, for example, 2 to 10% of iron, nickel, cobalt or aluminum as an alloy partner.
• Composite parts made of steel and zinc may also be considered here.
• Corresponding composite parts made from body steel and aluminum or from steel and aluminized steel - preferably fire-aluminized steel - are also used.
• Such cleaning solutions generally contain surface-active substances, such as wetting agents and emulsifiers, and so-called builder substances, for example sodium hydroxide, alkali metal carbonates, alkali metal phosphates, such as orthophosphates and corresponding condensed phosphates, for example sodium pyrophosphate or sodium triphosphate, for strengthening the emulsifying, saponification and dirt-carrying capacity optionally also silicates and borates.
• surface-active substances such as wetting agents and emulsifiers
• builder substances for example sodium hydroxide, alkali metal carbonates, alkali metal phosphates, such as orthophosphates and corresponding condensed phosphates, for example sodium pyrophosphate or sodium triphosphate, for strengthening the emulsifying, saponification and dirt-carrying capacity optionally also silicates and borates.
• builder substances for example sodium hydroxide, alkali metal carbonates, alkali metal phosphates, such as orthophosphat
• the cleaning and degreasing solutions as well as the phosphating solutions are usually applied to the metal surfaces to be treated in a spray, dip or combined spray-dip process.
• the workpieces - including the composite parts discussed above - are usually cleaned after cleaning or degreasing Rinsed water and then subjected to a phosphating process in a known manner. If necessary, however, the activation can also take place after the cleaning and degreasing stage in a separate process step.
• the cleaned and phosphated workpieces, i.e. automobile bodies are then painted, usually using the electro-dip painting process.
• the metals zinc and aluminum contained in the composite parts discussed above dissolve due to their amphoteric character both in acids and in bases with evolution of hydrogen. In the pH range from. 7 to about 12.5, however, these metals are considered to be relatively stable, since the dissolution of the metal surface is reduced by the formation of protective layers thereon.
• the commonly used alkaline cleaning solutions are in the previously mentioned pH range, so that no corrosion problems would be expected here. In practice, however, it has been shown that with the composite construction described above - conductive composite - corrosion of the zinc and aluminum surfaces also occurs in the pH range which is considered to be harmless. This results in punctiform, pitting-like corrosion phenomena as well as extensive damage to the zinc or aluminum surfaces.
• the object of the present invention is therefore to develop a method for cleaning and degreasing and activating composite parts made of steel and galvanized or aluminized steel prior to phosphating, in which the corrosion phenomena described above, due to the use of alkaline and also weakly acidic cleaning - and degreasing solutions - are avoided.
• the flow according to the invention completely prevents the flow of galvanic currents - and thus the occurrence of corrosive phenomena.
• the bath container made of steel of the cleaning or degreasing bath can serve as a counter electrode to the composite part. If, for example, bath containers made of non-conductive material - plastic are used in the process, an electrode made of sheet steel is introduced into the cleaning bath and the counter potential is built up between this and the composite part. In the sense of the method according to the invention, however, an electrode additionally arranged in the bath can also be present in a steel bath container. It is only essential to the invention that a counter potential is present between the composite part on the one hand and the bath container and / or additional electrode on the other hand, both composite both the part and the electrode are in contact with the bath liquid.
• customary cleaning and degreasing solutions can be used which have a pH in the range from 6 to 13.
• cleaning solutions which may have the ingredients listed above.
• phosphates, carbonates, borates, silicates or hydroxides of alkali metals are suitable as builder substances.
• Corresponding ammonium compounds can also be used for this.
• Further constituents of the cleaning solutions to be used according to the invention are customary anionic, cationic or nonionic wetting agents and emulsifiers. Of these, however, the nonionic types are preferably used, for example addition products of ethylene oxide with fatty alcohols, alkylphenols, fatty amines or polyoxypropylene glycols.
• hydroxypolycarboxylic acids such as citric acid
• aminopolycarboxylic acids such as nitrilotriacetic acid or ethylenediaminetetraacetic acid
• phosphonic acids such as ethane-1-hydroxy-1,1-diphosphonic acid or aminotrimethylenephosphonic acid
• the layer refiners and activators for example titanium orthophosphate, which are customary and known for this purpose, can also be added to the cleaning solutions.
• the method according to the invention can be used in the usual standing baths or also in the continuous systems frequently used in the automotive industry.
• the cleaning solutions can be applied either by immersion or spraying or in a combined spray-immersion process.
• the composite parts are treated with solutions which have a pH in the range from 7 to 11.
• the temperature of the aqueous cleaning and degreasing solutions should preferably be in the range from 35 to 70.degree.
• the composite parts are treated with a 0.1 to 3 percent by weight aqueous solution containing 72.5 percent by weight sodium tetraborate x 10 H 2 0 18 percent by weight sodium dihydrogen orthophosphate and 9.5 percent by weight of an addition product Contains 10 moles of ethylene oxide in nonylphenol.
• a counter potential is applied which is at least twice as high as the potential which arises due to the voltage series in the solution in question. In this way, possible fluctuations in the potential that is established can be absorbed, so that constant potential measurements for monitoring purposes are unnecessary.
• the phosphating and the subsequent painting of the composite parts or workpieces takes place in the customary manner.
• the cleaning solution was in a bath tank made of structural steel.
• a composite workpiece made of electrolytically galvanized steel and steel material No. 11 405 body steel
• a potential of 655 millivolts was measured.
• a potential of 575 millivolts was measured when immersing a corresponding composite workpiece with hot-dip galvanized steel (sendzimir-galvanized steel, redressed).
• a bath container made of non-conductive material (plastic) was used.
• the previously mentioned cleaning solution was used as the electrolyte under the conditions mentioned.
• a steel sheet was immersed in the bath solution as an additional electrode.
• a potential of 193 millivolts was measured between the composite workpiece made of body steel and electrolytically galvanized steel, which was immersed in the cleaning bath. Signs of corrosion on the galvanized steel were clearly visible.
• "counter potentials of 400 millivolts, 500 millivolts and 1,000 millivolts were applied. With all the cathodic counter potentials mentioned, there were no visible signs of corrosion on the electrolytically galvanized steel after 5 minutes of immersion in the cleaner.
• a counter potential of 400 millivolts was applied when using composite workpieces made of body steel and hot-dip galvanized steel. No signs of corrosion occurred after the same dive time. Even subsequent layer-forming phosphating of the samples treated according to the invention - in a phosphating bath containing zinc oxide, phosphoric acid and nitric acid - resulted in completely defect-free zinc surfaces; whereas the corrosion damage clearly appeared in the samples not pretreated according to the invention.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Electrochemistry (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Chemical Treatment Of Metals (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=6160839

Family Applications (1)

Country Status (3)

Cited By (7)

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• 1982
  • 1982-04-14 DE DE19823213649 patent/DE3213649A1/de not_active Withdrawn
• 1983
  • 1983-04-02 EP EP83103267A patent/EP0091627A3/fr not_active Withdrawn
  • 1983-04-14 JP JP6681683A patent/JPS58189375A/ja active Pending

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